As is generally well known, trucks for railway cars and, more particularly, freight railway cars are available in two design types. The first design type employs an H-frame that combines bolster and side frames into one component. This H-frame is connected to the wheel-set axles by way of helical coil springs, friction/viscous dampers and pedestals. This arrangement is widely known in the railroad industry as a primary suspension truck.
Another design type employs a 3-piece construction, wherein the bolster is oriented laterally between two longitudinally disposed side frames. The side frames in turn are connected to two wheel-set axles by way of bearing adapters and bearings. Main suspension elements include helical coil springs and friction wedge dampers, which connect the bolster and the side frames. This arrangement is widely known in the railroad industry as a secondary suspension of the truck.
Either truck design type is mounted for movement in vertical, lateral and longitudinal directions in order to accommodate various operational conditions.
The disadvantage of either the primary suspension truck or the secondary suspension truck is that when the truck is forced to move in any one direction, the coil spring groups, due to an inherent stiffness, also generate forces in the remaining two directions. Accordingly, prior to the present invention, some trucks enable operation of the railway car up to speed of 110 mph. Above this speed, the trucks become directionally and, more particularly, laterally unstable resulting in increased wear of the wheels, rails and truck components and potentially causing unsafe operations, including derailment. Such lateral instability is commonly known as hunting oscillation.
Lately, there is a growing need for a high-speed freight transport in the railroad industry wherein the railway cars would need to travel at speeds greater than 110 mph. Therefore, there is a need for an improved truck that allows high-speed operation of the railway car at speeds greater than 110 mph and without lateral instability of the presently available trucks.